This invention relates to a vapor recovery system and method for use in connection with a gasoline dispensing system, and, more particularly, to such a system and method for detecting for leakage in the vapor recovery system.
In general, gasoline dispensing and vapor recovery systems include one or more dispenser units, with each unit being connected to an underground storage tank for gasoline. Each unit has one or more nozzles for dispensing the gasoline into a vehicle fuel tank, and passages are provided in each nozzle for collecting the vapor/air mixture from the vehicle tank. A return line is connected to the vapor/air mixture passage for delivering the collected vapor/air mixture back to the underground fuel storage tank.
These types of systems include passive systems that rely solely upon vapor/air mixture pressure within the fuel tank to force the vapor/air mixture through the vapor/air mixture return line. However, due to pressure losses and partial obstructions in the vapor/air mixture recovery line (sometimes caused by fuel splash-back or condensation), the vapor/air mixture pressure developed in the vehicle fuel tank is often insufficient to force the vapor/air mixture out of the vehicle tank and to the underground storage tank.
Active vapor recovery systems and methods have also evolved that employ a vacuum pump for drawing the vapor/air mixture from the vehicle tank and through a vapor/air mixture return line. Some of these systems, such as the system disclosed in co-pending patent application Ser. No. 08/515,484, assigned to the assignee of the present invention, provide a relatively powerful, continuously-operating, vacuum pump and a valve arrangement for connecting the various vapor/air mixture return lines to the vacuum pump. Other active systems, such as a system marketed by the assignee of the present invention under the "WAYNE VAC" designation, employ a vacuum pump at each dispenser unit which is connected to a vapor/air mixture return line. These systems have proven to be relatively easy to use and customer-friendly.
In these active vapor recovery systems, to insure optimal efficiency it is essential that there be no leakage of vapor from the vapor recovery system including the conduit connecting the dispensing nozzle(s) to the underground storage tank, and from the components connected to the conduit. However, there is no acceptable or reliable technique for detecting this type of leakage, especially a technique that can be utilized by a relatively unskilled person. Therefore, since a leakage of this nature can create significant system operational inefficiencies, it is important that a technique for sensing the leakage be available. In this context, it is also important that the vacuum pump perform at acceptable standards.
Therefore, what is needed is vapor recovery system and method of the above type according to which leakage in the system, as well as vacuum pump performance, can easily be sensed.